This invention relates to a screen fixing device of a projection type television (TV) system, and more particularly, to a screen fixing device detachably mounted to a front opening section of a multi projection type TV system comprising a plurality of projection type TV units arranged in matrix in vertical and horizontal directions.
In known technology, a multi projection type TV system having a large screen has been constituted by arranging a plurality of projection type TV units (called merely TV unit hereinlater) each having the same structure, each piled in matrix in the vertical and horizontal directions and each incorporating three cathode ray tubes (CRT) for three colors, i.e. red (R), green (G) and blue (B), and images from the CRTs are projected on the screen.
In a multi projection type TV system having the configuration as described above, it is generally known that a screen arranged in an opening section of a multi projection TV unit in a quickly removable manner is convenient for maintenance and inspection of components in the TV units such as CRTS. Also, by using a fixing frame, it is possible to absorb machining accuracy of a screen consisting of a Fresnel lens and a lenticular sheet or, in other words, a gap between the Fresnel lens and the lenticular sheet and the opening of the TV unit.
Conventionally, as shown in FIG. 15, a screen 6 consisting of a Fresnel lens 4 and lenticular sheet 5 is connected to a stopper piece 3 made of rubber and held in a front opening section 2 of a TV unit 1, and a fixing frame 7 is set around a front edge section of the screen 6 and then fixing screws 9 are screwed through holes 8 into taps arranged in two adjacent front opening frames 2a, 2a.
Accordingly, it is required to locate the two fixing frames having a width which allows absorption of changes in screen size due to machining accuracy or thermal expansion of the screen 6 in a fixed state of the screen 6. In a case where several tens of TV units are piled in matrix in vertical and horizontal directions, each unit can not be separated for the purpose of inspecting or repairing the same, but when it is required to check or repair components of the TV unit I such as CRTs without changing the TV system configuration, the components of the unit 1 can be checked or repaired by loosening the fixing screws 9, removing the fixing frames 7 and then removing the screen 6 from the front opening frames 2a of the TV unit 1. When the screen 6 of a certain TV unit 1 is broken, the screen can be replaced with a new one with the TV system being set.
In the conventional type of screen fixing device of the character described above, however, the cross section of the fixing frames have an approximately rectangular form and cover the end face of the front opening frames 2a of the TV units 1. Therefore, when a multi projection type TV system is seen from a front position at an angle (for instance at 45 degrees), a width of the two adjacent fixing frames 7 becomes a width Wb which is larger than a width Wa of the two adjacent fixing frames 7 in comparison with a case when viewed from the front side. This makes it difficult to clearly observe images on the screen. It is conceivable to reduce an area of the cross section of the two adjacent fixing frames 7 in order to solve this problem, but due to fixing force of the fixing screws 9 and strength of the fixing frames, there is a limit in reducing the cross section of the fixing frames 7.